1. Field of the Invention
The present invention is a method of high quality analog or digital signal transmission by wire generally in the sub-audio to video range by means of normal-mode current flow with suppression of normal-mode voltage amplitude.
2. Description of Prior Art
The transmission of audio signals is generally in the range of 5Hz-100kHz between electronic equipment that process or otherwise employ the signal. Generally such transmission is done by originating the signal from a low impedance and receiving it at a high impedance, often referred to as “voltage matching” or “bridging”. In some (usually large) systems such as telephony the source and receiving impedances are matched. This is also true in voltage based video transmission. This is seldom done anywhere else in contemporary audio practice, either consumer or professional. In all such systems the signal voltage is impressed across the dielectric (insulation) of the conductors. As a result, the properties of the dielectric may strongly affect the quality of the resulting received signal. Specifically, the attribute of dielectric absorption seems to impart an audible degradation.
Industrial control practice has for many years used another method for transmitting process signals over long distances. It is known as a current-loop. There are several variations of the technique, but the most common is known as a 4-20 mA current-loop. In this method of transmission, the signal is originated from a high impedance source and received by a low impedance receiver, essentially the opposite of voltage matching mentioned above. Generally the bandwidth of 4-20 mA loops is not high enough to support audio applications, but there is nothing inherent in the technique which precludes greater bandwidth. Industrial current-loops generally allow the reporting of a DC value and this is not necessary for audio or video, which are AC signals. This permits a different approach to current-based signal transmission.